The present invention generally relates to battery packs and battery charging systems.
Battery packs consist of a plurality of electrochemical devices. Electrochemical devices comprise such devices as rechargeable batteries, fuel cells, double layer capacitors, and a hybrid battery containing fuel cell electrode and electrochemical supercapacitors. Battery cells are electrochemical devices that store energy in chemical form. A rechargeable battery cell is capable of storing electrical charge in the form of a reversible chemical reaction. When the battery cell is subsequently placed across a load, this reaction reverses from the direction in the storage mode, thereby producing electrical energy for use by the load. Rechargeable battery packs, also known as secondary batteries, are widely used as a power source for many devices. The number and type of electrochemical devices comprising the battery pack determines the power rating of a battery pack. A battery pack may consist of rechargeable battery cells in series, in parallel, or in series and parallel. To obtain a battery pack consisting of rechargeable battery cells which has a higher voltage than a single cell""s voltage, typically a plurality of cells are placed in series, while to obtain a battery pack that has a higher capacity than a single cell""s storage capacity, typically a plurality of cells are placed in parallel.
Those skilled in the art understand battery cell life and performance can be enhanced with battery cell conditioning. Battery cell conditioning occurs when the battery cell is discharged in a predetermined sequence in relationship to the recharging of the battery cell. Prior art further teaches us the benefits of pulse charging and discharging. U.S. Pat. No. 5,633,574 entitled xe2x80x9cPulse charge Battery Chargerxe2x80x9d, issued to Sage on May 27, 1997 provides enhanced battery conditioning capability with pulse charging and discharging, and is hereby incorporated by reference. In order to accomplish the discharge pulse for battery pack conditioning, current from the battery pack must flow in the reverse direction, that is, from the battery pack to a load included in the battery charger. However, not all battery packs are capable of allowing a discharge pulse through all of their terminals.
Battery packs may include short circuit battery terminal protection preventing a conditioning reverse current flow from occurring through these terminals. Unprotected battery terminals may themselves come in contact with foreign objects, which can cause a battery pack to short circuit, spark, or cause the terminals to overheat. To deal with this problem, battery packs may include two sets of terminals or connectors, one unprotected operatively accessible by the battery powered device and one set of terminals accessible to an external power source for battery charging. This external set of charging terminals may be short circuit protected or unprotected. Alternatively, battery packs with two sets of terminals can be located within the battery powered device, with one set of terminals operatively coupled to or positioned adjacent to a set of terminals located in the housing of the device, which are themselves accessible to an external power source for battery charging.
The present start of the art for passively protecting battery pack terminals from an externally induced short circuit uses a conventional blocking diode operatively coupled to the battery terminals. However, the conventional blocking diode conducts current in only one direction, thereby preventing the discharging of the battery pack through these terminals. This type of battery pack protection requires a battery charging system using a discharging means for conditioning of battery packs to be operatively coupled to a set of unprotected battery pack terminals or connectors, therefore requiring the removal of the battery pack with protected external terminals from the battery powered device to expose the unprotected terminals or connectors and then, once removed from the device, further requiring the user to operatively couple the battery pack to the battery charging system. These charging systems require the user to take the time to execute this operation, and take more time to replace the battery pack on the battery powered device once battery charging and conditioning is completed, thereby adding to the total labor time and costs associated with using battery powered devices and in the case of emergency personnel such as firefighters, adding to their overall emergency response time as well.
Prior art has addressed the lack of discharge capability of the conventional blocking diode passively protected battery pack by adding an active means of xe2x80x9cturning onxe2x80x9d and xe2x80x9cturning offxe2x80x9d an electronic device included in the charge path of the battery pack. xe2x80x9cU.S. Pat. No. 5,710,505xe2x80x9d shows us a battery pack with short circuit protection which allows both charging and discharging. xe2x80x9cU.S. Pat. No. 5,710,505xe2x80x9d uses a Triac device in the charge path of a battery pack and operationally requires a battery pack with a minimum of three terminals. The Triac device, when actively xe2x80x9cturned onxe2x80x9d, allows the conduction of current through the device. However, a limitation of a Triac device is that once the device is in an xe2x80x9con statexe2x80x9d, that is, conductive, the current through the device must be interrupted, or drop below a minimum holding current, to restore the non-conductive xe2x80x9coff statexe2x80x9d condition, thereby restoring the short circuit protection. Therefore, unless the current in xe2x80x9cU.S. Pat. No. 5,710,505xe2x80x9d is reduced to the minimum level or completely interrupted, the reverse current non-conductive battery short circuit protection will not be restored. This same operational limitation which applies to a triac device likewise applies to a Thyristor. Field Effect Transistors (FETs) and Metal Oxide FETs (MOSFETs) devices also must be xe2x80x9cturned onxe2x80x9d to conduct current, but then must be actively xe2x80x9cturned offxe2x80x9d to restore the non-conductive state, thereby restoring the battery pack short circuit protection.
In addition to devices such as Triacs and Thyristors, current flow can also be controlled using voltage clamping devices, which include but are not limited to, Zeners, Transient Voltage Suppressors (TVS), and Metal Oxide Varistors (MOV). Voltage clamping devices have a reverse voltage breakdown threshold; that is, allowing the conduction of a reverse current flow without restriction through the voltage clamping device, given enough reverse voltage is applied, then automatically restoring to a non-conducting mode when the voltage drops below the breakdown threshold. Depending on operating conditions, the breakdown threshold of the voltage clamping device may be due to an avalanche type junction breakdown or a tunneling type junction breakdown or a combination of both. This voltage breakdown threshold is a well-defined reproducible operating characteristic of the device. The classic voltage-current interrelationship diagram for voltage clamping devices is depicted in FIG. 4 of the accompanying drawings.
Each voltage clamping device will have an optimum operating voltage range and will exhibit predictable operating variations such as reaction time, variation in reverse current leakage, and variations in device failure mode and device failure frequency. The useful life of the voltage clamping device in the battery pack is dependent on the correct voltage clamping device selection for the specific battery pack application. Voltage clamping devices are further characterized by specifying the maximum clamping voltage at the maximum reverse current rating. Silicon voltage clamping devices incorporating a larger junction cross section are also known as Transient Voltage Suppressors (TVS) and will survive a large number of reverse current draws, given the appropriate operational environment.
The overall useful life, that is, survival capability under a particular load for a specific time period, of the voltage clamping device can be maximized with the careful determination of the applications"" operating conditions and the operating performance of the specific voltage clamping device in those conditions. Operating parameters such as the voltage, current flow and periodicity of the transient voltage event must be considered. The voltage clamping device operating characteristics can be further enhanced when used in parallel or in series with each other and with other electronic components, comprising but not limited to Schottky diodes, conventional blocking diodes and conventional resistors.
Temperature is another key operating variable to consider when selecting a voltage clamping device for the specific battery pack application. Heat within the battery pack can result from excessive ambient temperature, battery cell self heating and voltage clamping device self heating effects from applied power. Junction performance of a voltage clamping device will vary in relation to temperature, with excessive heating directly impacting the voltage clamping device useful life. Therefore, for a given operating application, performance and useful life of the voltage clamping device can be enhanced, if exposure to excessive operating temperature is avoided. Those skilled in the art understand that battery cell life and therefore battery pack life will likewise be enhanced if exposure to excessive operating temperature is avoided.
Potential exposure to excessively high temperature during the operation of the battery pack can be minimized by the addition of a means to detect temperature in its operating environment by providing a means for obtaining operating temperature feedback information. Furthermore, it can be expected that the heat generated by operating various electronic and electrochemical devices in the battery pack internal environment will not be the same due to differences in device operating characteristics, manufacturing differences between similar devices, and age differences of similar devices. Within a battery pack, these differences in thermal characteristics will result in a heterogeneous distribution of temperature gradients within the battery pack internal environment during battery pack charging and discharge, therefore potentially distorting available battery pack temperature information and the available device specific temperature information. Battery pack internal temperature information errors may also occur from the imperfect contact between the temperature detection means and the material requiring temperature measurement.
Differences in temperature gradients can be passively compensated in part by the thermal conductivity of the specific electronic components themselves as well as their surrounding environment; in the case of a battery pack air surrounding the battery cell and battery cell to battery cell contact. In effect, one battery cell may act as a heat sink for its neighbor. Additionally, a heat generating electronic component may be passively protected from excessive heat and/or thermal gradients in an electronic device passively protected by the use of a xe2x80x9cheat pipexe2x80x9d type of component, where heat is transferred from a heat source to a heat sink. These thermal gradients can be reduced from general or specific areas within the electronic device. Heat pipes are vacuum tight vessels that rely on a continuous cycle where liquid evaporation occurs at the heat source, thereby absorbing thermal energy, with the resultant higher pressure vapor traveling to the heat sink, and where condensation at the cooler heat sink end then occurs, thereby releasing the thermal energy absorbed at the heat source. The condensed fluid within the heat pipe is then returned to the heat source area by capillary action. Therefore, a heat pipe is a passive means to protect, to the capacity of the heat pipe, from excessive heating of components within an electronic device. Heat pipes may be operatively coupled to the heat generating components of a system or located proximate to the heat generating components using air or other gas medium as an intermediate thermal conductor.
This summary of invention provides a reference to the various embodiments of the passively protected battery pack with on load charge and on load conditioning-discharge capability and charging system. Accordingly, improved battery pack protection with on load charge and discharge capability has been provided, which can be incorporated into a charging system with a minimum number of only 2 terminals. The ability to provide a passively protected on load charge and on load conditioning-discharge capable battery pack with charging system will be a significant time saver to those individuals who work with the system by eliminating the need of removing the battery pack from the battery powered device to charge and conditioning-discharge, while the short circuit safety of the individual and the battery pack is maintained at all times at the passively protected terminals. Further, the passively protected battery back with on load and on load conditioning-discharge capability will be an enhancement to the overall charging system because of improved mechanical integrity, ease of manufacturing, lower component count and lower associated production costs.
While the summary of the passively protected battery pack with on load charge and on load conditioning-discharge capability has been described in connection with what is presently considered to be the most practical and preferred embodiments, it is to be understood that the passively protected battery pack with on load charge and on load conditioning-discharge capability is not to be limited to the disclosed embodiments. On the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.
Passively Protected Battery Pack with On Load Charge and On Load Conditioning-Discharge Capability and Charging System
The object of the passively protected battery pack with on load charge and on load conditioning-discharge capability and charging system is to provide a passive means of protecting a battery pack with a plurality of battery cells from an externally induced short circuit of the battery pack with a minimum of 2 terminals. A battery pack may still be connected to a load such as a cellular phone, while the battery cells are being charged or discharged with at least the battery pack external terminals passively protected from a damaging short circuit occurring at any time. How a battery is protected, and how the battery is charged, in one embodiment centers on a protective means, also referred to one voltage clamping device, in the charge path of the battery pack, which in this embodiment is a silicon transient voltage suppressor. The appropriate operating value of at least one voltage clamping device is selected for the battery pack, given the battery pack voltage, battery pack amperage and environmental operating conditions.
It would be highly desirable to have a battery pack with short circuit protection and a charger system capable of providing both charging and discharging capabilities through a reduced number of terminals, the minimum number being 2. Reducing the number of terminals required in a charging system while still providing passively maintained short circuit protection for the battery pack and its cells, while at the same time providing both on load charging and on load conditioning-discharging capability, would be an enhancement to the overall charging system in terms of providing the capability of conditioning the battery pack while the battery is still connected to the battery powered device. A 2 terminal passively protected battery capable of providing both on load charging and on load conditioning-discharging capability would further be an enhancement to the overall charging system because of the improved mechanical integrity, safety, ease of manufacturing, lower component count and lower associated production costs.
Passively Protected Battery Pack with On Load Charge and On Load Conditioning-Discharge Capability with Charge Only Battery Charging System
The object of the passively protected battery pack with on load charge and on load conditioning-discharge capability is to provide a passive means of protecting a battery pack from an externally induced short circuit and to provide both charge and discharge capability while requiring only 2 terminals. This is accomplished by utilizing at least one voltage clamping device in the charge path of the battery pack.
Because of the improved mechanical integrity, safety, ease of manufacturing, and lower component count and costs, it would also be highly desirable to have a short circuit protected battery pack with a reduced number of terminals, the minimum number being 2, that could be charged using a battery pack charger even though the charger lacked the ability to condition-discharge the battery by use of a discharge feature.
Passively Protected Battery Pack With On Load Charge and On Load Conditioning-Discharge Capability and Pulse Charging System
In a further embodiment of the passively protected battery pack with on load charge and on load conditioning-discharge capability, a pulse charging and discharging means is added within the battery charger system for enhanced conditioning of the battery cells in the battery pack. By utilizing the voltage clamping device in the charge path of the battery pack, this eliminates the need for removing the battery pack from the battery powered devices for enhanced pack conditioning, comprising, but not limited to, cellular phones, two way radios, portable power tools and other battery powered devices, thereby further extending battery cell useful life, improving battery pack life, improving mechanical integrity, safety, ease of use, and reducing labor time and labor costs associated in removing and replacing battery packs from battery powered devices for enhanced battery cell conditioning.
Passively Protected Battery Pack with On Device Charge and Conditioning-Discharge Capability With Enhanced Operating Characteristics and Charging System
By means of a further embodiment of the passively protected battery pack with on load charge and on load conditioning-discharge capability, the operating characteristics of the voltage clamping device in the charge path of the battery are enhanced by means of additionally including at least one resistor in the charge path of the battery to limit current flow through the voltage clamping device, thereby enhancing the voltage clamping device survival rate in the battery pack, and thereby improving the battery pack survival rate by protecting it from an accidental excessively high charging current or excessively high conditioning discharging current operating event.
By means of a further embodiment of the passively protected battery pack with on load charge and on load conditioning-discharge capability, the operating characteristics of the voltage clamping device in the charge path of the battery are enhanced by means of additionally including at least one conventional blocking diode in parallel with the voltage clamping device in the charge path of the battery, thereby enhancing the voltage clamping device failure characteristic by continuing to provide a charge current path to the battery cells from the battery pack charging system in the event of an operational failure of the voltage clamping device, thereby enhancing the useful life of the battery pack.
By means of a further embodiment of the passively protected battery pack with on load charge and on load conditioning-discharge capability, the operating useful life of the voltage clamping device in the charge path of the battery is enhanced by means of additionally including at least one Schottky diode in parallel with the voltage clamping device in the charge path of the battery. The Schottky diode forward voltage characteristic is less than that of the voltage clamping device and therefore the charging current will flow with a preference through the Schottky diode, thereby reducing the forward current stress on the voltage clamping device, thereby enhancing the useful life of the voltage clamping device, thereby enhancing the useful life of the battery pack.
Passively Protected Battery Pack with On Load Charge and On Load Conditioning-Discharge Capability With Enhanced Internal Battery Pack Information and Charging System
By means of a further embodiment of the passively protected battery pack with on load charge and on load conditioning-discharge capability, a detection means is added within the battery pack for detecting a temperature within the battery pack, and a temperature detection terminal that transmits temperature information indicating the temperature detected by the temperature detection means to the charging/discharging device, thereby enhancing the available internal battery pack information to the battery pack charging system.
By means of a further embodiment of the passively protected battery pack with on load charge and on load conditioning-discharge capability, a temperature detection means is added within the battery pack which is operatively coupled to thermally conductive material located adjacent to a plurality of battery cells for detecting a temperature within the battery pack, and a temperature detection terminal that transmits temperature information indicating the temperature detected by the temperature detection means to the charging/discharging device. The thermally conductive materials will passively modify the temperature information that is collected by the temperature detection means according to the thermal characteristics of the material such as its thermal conductivity, thereby enhancing the available internal battery pack information to the battery pack charging system.
Passively Protected Battery Pack with On Load Charge and On Load Conditioning-Discharge Capability with Enhanced Internal Passive Thermal Protection and Battery Pack Information and Charging System
By means of a further embodiment of the passively protected battery pack with on load charge and on load conditioning-discharge capability, a passive thermal protection means, in this case, at least one heat pipe, is added within the battery pack for passively protecting the voltage clamping device from excessive heating events and for minimizing the temperature gradients within the battery pack during battery pack cell charging and battery cell conditioning-discharging, thereby enhancing the operating conditions of the voltage clamping device within the battery pack and thereby the overall useful life of the voltage clamping device, as well as the overall battery pack life.
By means of a further embodiment of the passively protected battery pack with on load charge and on load conditioning-discharge capability, a passive thermal protection means, in this case, at least one heat pipe, is used in combination with a temperature detection means added within the battery pack for detecting a temperature within the battery pack, and a temperature detection terminal that transmits temperature information indicating the temperature detected by the temperature detection means to the charging/discharging device, thereby enhancing operating conditions of the voltage clamping device within the battery pack and the available internal battery pack temperature information.
Those skilled in the art will understand by virtue of the improved mechanical safety that it would be highly desirable to have a battery pack with a passive thermal protection means, in this case at least one heat pipe, even if the charging system lacked the ability to condition-discharge the battery by use of a discharge feature.
Passively Protected Battery Pack With On Device Charge and Conditioning-Discharge Capability With External Passive Protection Placement
By means of a further embodiment of the passively protected battery pack with on load charge and on load conditioning-discharge capability, where the battery pack with multiple sets of terminals is located within the battery powered device, where one set of terminals, whether passively protected or unprotected is operatively coupled to or positioned adjacent to a set of terminals located in the housing of the battery powered device, which are themselves passively protected with at least one voltage clamping device in the charge path of the battery pack and which battery housing terminals themselves are accessible to an external power source for battery charging, thereby enhancing passive protection of the battery pack located in the battery operated device at all times, enhancing the ease of manufacturing, thereby lowering associated production costs and providing enhanced safety.
Passively Protected Battery Pack With On Load Charge and On Load Conditioning-Discharge Capability Consisting of a Plurality of Electrochemical Devices and Charging System
By means of a further embodiment of the passively protected battery pack with on load charge and on load conditioning-discharge capability and charging system, a plurality of electrochemical devices comprising such devices as rechargeable batteries, fuel cells, double layer capacitors, and a hybrid battery containing fuel cell electrode and electrochemical supercapacitors are included within the battery pack for enhancing the charge and discharge operating characteristics of the overall battery pack.
The benefits of the passively protected battery pack consisting of a plurality of electrochemical devices and charging system with a reduced number of terminals, the minimum number being 2, are improved mechanical integrity, enhanced pack safety from short circuits, and lower component count and lower costs.